I think the fundamental flaw is the statement that metascores or any other review or review total or average is objective. Reveiws, all reviews, are opinion. Opinion is by definition subjective.
We all have different views on what makes something good or of high quality. When it comes to games, I think all that matters is whether it is enjoyable. Sales are as good a measure as anything, because if a lot of people buy it presumably a lot of people enjoy it. But high sales doen't mean something is universally better for every consumer.